This invention relates to improvements in exterior finishing systems such as, for example, exterior insulation and finish systems (EIFS) and direct-applied exterior finish systems (DEFS) for buildings. Such EIFS systems are fully described in U.S. Pat. No. 4,647,496. More particularly, this invention relates to an improvement in the management of water as a line of defense by harmlessly handling any unwanted water that has penetrated behind the exterior cladding.
Originally, EIFS was an exterior wall concept designed to have high insulation values and a reliable stucco finish that could be economically created in a wide array of textures and colors. It immediately became successful because it provided so much performance for so little cost. The most unusual aspect of the system was that expanded polystyrene (EPS) insulation was installed on the exterior side of the wall by adhesively bonding it to a substrate, forming a base for an exterior coating as well as adding more insulation to the building. The surface typically has a 1/8-inch-thick synthetic-stucco finish system which performs two functions. It is designed to (1) provide a face-seal or barrier to seal out moisture and (2) provide a decorative finish at the same time. This 1/8-inch-thick finish system consists of reinforcing mesh, latex-fortified basecoat, and an aggregated, polymeric, textured finish.
The principal weaknesses in the prior art EIFS is that they have only one line of defense against water intrusion and no means to drain intruding water. Although the surface usually forms an effective water barrier, intersections of the surface with other elements, such as window frames, door frames, etc., often leave gaps or openings that driving rain can penetrate. Once inside the sealed wall and behind the cladding, the water can remain trapped long enough before evaporating to damage or rot any water-sensitive elements, to which the insulation is bonded including, oriented-strand board, plywood, or gypsum sheathing.
Whether the prior art exterior wall systems provide an insulation layer attached to the exterior cladding which is coated with a stucco-look finish (EIFS), or the stucco-look finish is applied directly over the cladding (DEFS), there has been no provision for water managed relief at the back side of the cladding.
As a result of these problems, a need has arisen for water-managed exterior finishing systems. The present invention discloses an exterior wall system that includes a drainage medium on the outer surface of a weather-resistive membrane. This system provides the designer and building owner with a combination of the optimal properties of a weather-resistive membrane with the long-term reliability of water management.